LTE Planning & Design Guidelines
1.
Introduction ...........................................................................................................................................................3
2.
PCI Planning Strategy ...........................................................................................................................................3
3.
RSI Planning .........................................................................................................................................................4
4.
Tracking Area Planning ........................................................................................................................................6
5.
Transmission Modes .............................................................................................................................................8
6.
LTE Interworking Strategy ...................................................................................................................................8
6.1
Objective ......................................................................................................................................................8
6.2
Idle Mode Layering Strategy........................................................................................................................9
6.2.1
Cell Selection ...........................................................................................................................................9
6.2.2
Cell Re-selection .................................................................................................................................... 10
6.2.2.1
Intra frequency Cell Re-selection ...................................................................................................... 10
6.2.2.2
Inter Frequency and Inter RAT Cell Re-selection ............................................................................. 11
6.3
Connected Mode Layering Strategy ........................................................................................................... 13
6.3.1
Intra LTE Handover ............................................................................................................................... 13
6.3.2
Inter RAT Data Handover...................................................................................................................... 14
6.3.2.1
Inter RAT Handover - LTE to GSM ................................................................................................. 14
6.3.2.2
Redirection without Measurements - LTE to GSM ........................................................................... 15
6.4
LTE Voice .................................................................................................................................................. 13
6.4.1
CSFB to 2G............................................................................................................................................ 15
6.4.2
Fast return to LTE .................................................................................................................................. 15
7.
Paging ............................................................................................................................................................. 17
8.
Volte ............................................................................................................................................................... 18
8.1
Volte Architecture ...................................................................................................................................... 18
8.2
Volte Bearer combination .......................................................................................................................... 18
8.3
Volte Parameter.......................................................................................................................................... 19
9.
SRVCC ........................................................................................................................................................... 20
9.1
SRVCC to GSM ......................................................................................................................................... 20
1. Introduction
This document covers the key parameter planning strategy and interworking details for BSNL India LTE
Network. The recommendations mentioned in this document are based on best practices being adopted in
Nokia Global LTE NW implementations. This document will serve as reference for further discussions and
optimizations at BSNL India LTE Networks.
2. PCI Planning Strategy
General
PCI (Physical Cell Identity) is used to identify the cell. There are 504 unique physical layer cell identities.
The allocation of physical layer cell identities is analogous to scrambling code planning for UMTS. The
isolation between cells which are assigned the same physical layer cell identity should be maximised to
ensure that UE never simultaneously receive the same identity from more than a single cell.
PCI planning of small network with few cells is easy task to perform manually. However bigger network
needs use of an automated planning based on the allocation rules along with minimum re-use distance
concept. This task can be handled by 3rd party tools such as Atoll/Asset or Vendor properietry tools. All
tool requires propagation files as input to create PCI Plan.
PCI Planning Strategy
•
•
•
•
•
•
Available PCIs are divided in 4 Groups
Every group contains 114 PCIs
Out of 114 PCIs, 24 PCIs are kept for future use for infill sites within specific group
Any LTE site being planned will always be part of one of the PCI groups (group identified by
specific color in map)
A database will be maintained for quick reference of a site and its PCI group
Some PCIs (remaining 48) are reserved for special purpose (micros, more than 3 sectors, special
events, troubleshooting etc.)
Key Benefits
•
Operational benefit for optimization engineer since one group will be used in single geography
•
•
•
Easy to maintain geographical distance between two groups
Caters to future expansion with in group
PCIs reserved for special usage will be helpful for more than three sector sites
Below rules to be followed during PCI planning
• Sectors of a site should never have same PCI
• Sectors of a site should not have PCI Mod 3 clash (3 sector site)
• Avoid PCI Mod 3 clash for nearby neighbor cells to maximum possible extent
• For new sites, ensure reusing the PCIs from the specified group only
Planned PCIs are reused in specific clusters after certain distances to avoid PCI and PCI Mod 3 clash.
3. RSI Planning
Random access is a basic procedure within cellular technologies so the terminal establishes uplink
synchronization and starts the uplink transmission. In LTE, the random access is used for several purposes,
some of them:
•
•
•
Initial access when establishing a radio link
To re-establish a radio link after a radio link failure
During the handover process
Before starting the random acess process the UE has already adquired downlink synchronization. The UE
selects randomly a preamble from a list of parameters broadcasted in BCCH and transmits it in the PRACH
with an initial power. If the random access atempt is unsuccesful (there is no answer from the eNB) the UE
makes a retry with higher power level
Upon the reception of the preamble the eNB assigns a UL capacity grant so the UE can send the information.
DL
PRACH Response
Not detected
Next PRACH
Resource
UL
Preamble
UE Specific Data
Preamble
There are 64 preamble sequences available in each cell and are grouped in subsets, the terminal randomly
selects one sequence in one of the subsets during random access process.
The preamble consists of two parts: the preamble sequence and the cyclic prefix. In addition, there is a
guard time used during the preamble transmission to account for the timing and avoid interference with
other subframes not used for random access.
Based on the duration of the cyclic prefix and the preamble sequence 4 different preamble formats are
defined in LTE FDD. Most commonly used preamble format is Configuration 0 that allows for maximum
cell ranges of up to 15 KMs. The preamble configuration used in a cell is transmitted as part of the system
information
Preamble signatures generated from a cyclic shift of a single root sequence are orthogonal. The cyclic shift
is used for preamble generation and the configuration determines how many cyclic shifts are needed to
generate the preamble. We are using Preamble format 0.
RSI Planning Strategy
When two cells that are assigned the same root sequence could interfere each other and potentially lead to
ghost RACH’s, therefore the set of logical root sequence index assigned to each cell should be planned in
a way to avoid re-use in neighbor sites.
The relationship between cell size and the required number of root sequences allows for system
optimization. Ncs value to be chosen based on the inter-site distances across circles. Example, for Metro
city, inter-site distances are too less, hence we have chosen Ncs as 38 which ensures to have cell range of
4.5 km.
General guideline for Nokia circles are as follows.
• NCs 8, Cyclic Shifts 46, cell range ~6 KMs
Distribution of available 838 RSIs will be as follows and this will be common for all circles.
• Out of 838 available RSIs, 720 RSIs to be used
• 720 RSIs are divided into 4 RSI groups. Certain RSIs within each group are reserved for infill sites
•
80 RSIs are reserved for future (infill sites)
• 35 RSIs are reserved for special purpose
• RSI for any LTE site being planned will always belong to one of the 4 RSI groups
• Use RSI from Spare only if it is not possible to reuse from the specific site RSI group
• Use RSIs from special group for sites with more than 3 sectors, special event sites, troubleshooting
purpose etc.
RSI Group
RSIG1
RSIG2
RSIG3
RSIG4
Micro + Spare
Special Purpose
RSI Range
1 to 144
181 to 324
361 to 504
541 to 684
721 to 800
801 to 837, 0
Future Usage
145 to 180
325 to 360
505 to 540
685 to 720
Yes
Yes
4. Tracking Area Planning
Tracking Areas (TA) represent the LTE equivalent to Routing Areas. LTE does not have a circuit switched
domain so does not require Location Areas. TA are used for Evolved Packet System (EPS) Mobility
Management (EMM). UE are responsible for registering themselves within specific TA. System
Information Block 1 broadcasts the TA to which a cell belongs. An eNodeB can include cells which belong
to different tracking areas.
Once a UE is registered within a specific TA then paging messages are broadcast across all cells belonging
to that TA. The normal TA updating procedure is used when a UE moves into a TA within which it is not
registered.The periodic TA updating procedure is used to periodically notify the availability of the UE to
the network .
The Tracking Area Identity (TAI) is constructed from a concatenation of the Mobile Country Code
(MCC), Mobile Network Code (MNC) and Tracking Area Code (TAC). The TAC has a length of 16 bits,
allowing 65,536 TAI per PLMN.
TA boundaries should not run close to and parallel to major roads nor railways otherwise there is a risk of
relatively large numbers of updates. Likewise, boundaries should not traverse dense subscriber areas.
Cells located at a TA boundary and which experience large numbers of updates should be monitored to
evaluate the impact of the update procedures. In LTE, location update happens in Tracking Area List
(TAL).
TAL is comprising of multiple Tracking Area Code (TAC).
Nomenclature
For CSFB, TAL should be mapped to underlying 3G/2G LA. There may be multiple TACs with in one
Tracking Area List.
Tracking Area Dimensioning
TA dimensioning is the process of finding a optimum number of eNBs in a Tracking Area. A smaller TA
size will lead to frequent TA updates due to mobility. This will increase signalling load and may reduce
the paging success rate.
On the other hand, by increasing the TA size, the frequency of tracking area update is reduced. However,
this will results in increased paging load.
The upper limit of the number of eNBs in a TA is determined by the paging capacities of the MME and
eNB.
Generally, following are the guideline w.r.t dimensioning.
•
Clutter
eNB per TA
TAs per TAL
Urban
30 ~ 50
1 TAL ~ 6TAs
Suburban
40 ~ 60
1TAL ~ 6TAs
Configured Site Count/ TAL has to be approx. 175 sites
Key points for TAC- LAC mapping
•
•
•
•
Each LAC will be mapped with one TAL
Each TAL can be comprised of single TAC or multiple TACs;
One or multiple TACs can be part of one LAC
Multiple LACs can’t be part of one TAC
Example for TAC – LAC Mapping
CELL
LAC
33302
33303
33306
33315
33316
33317
33318
33319
33320
33321
TAC 1
52002
52003
52006
52043
52016
52017
52050
52035
52020
52046
TAC 2
TAC 3
52044
52052
52015
52018
52036
52055
52045
52019
52021
TAC
LIST ID
TAL 1
TAL 2
TAL 3
TAL 4
TAL 5
TAL 6
TAL 7
TAL 8
TAL 9
TAL 10
5. Transmission Modes
3gpp has specified various transmission modes in the LTE Network for Tx diversity, MIMO and Beam
forming. With current FDD 2X2 deployment, following Transmission modes will be used during initial
deployment
TM Mode 2: Tx Diversity
TM Mode 3: Open loop Spatial Multiplexing - MIMO
Based on reported radio conditions by UE, eNB decides to switch transmission mode between TM2 and
TM3. Following are the radio parameters being set to make the change over happen.
Parameter
Value
mimoOlCqiThD
7
mimoOlCqiThU
8
Remarks
CQI threshold to fall back to Tx diversity
MIMO
CQI threshold to fall back to Open Loop
Spatial Multiplexing MIMO
6. LTE Interworking Strategy
With the introduction of LTE, existing networks will be operating with multiple RATs (LTE, UMTS and
GSM). This section provides guidance for mobility and traffic handling between following layers in a
network
• LTE FDD, 2100 MHz
• GSM 900 MHz
Broadly mobility strategy is divided into three parts
1. Idle mode
2. Connected Mode
3. Voice (CSFB)
6.1 Objective
With the introduction of LTE, existing networks will be operating with multiple RATs (LTE, UMTS and
GSM). This section provides guidance for mobility and traffic handling between following layers in a
network
• To ensure seamless interworking between all frequency bands and layers
• To distribute UEs between coverage and capacity layers
• To ensure that LTE capable UEs stay in LTE layer for most of the time provided coverage is
available
• Voice calls in LTE to be redirected to GSM900 using CSFB.
6.2 Idle Mode Layering Strategy
All LTE capable devices support absolute priority based cell selection and reselection. Absolute priority
can be defined from 0 (Lowest) to 7 (Highest). Recommended priority is defined in following order
•
•
LTD FDD (Highest)
GSM 900/1800 (lowest)
In the current network configuration, L2100 will have highest priority. Priority 7 & 6 can be used in future
if additional LTE bands are acquired by BSNL.
6.2.1
Cell Selection
Cell selection is based on RSRP and RSRQ as per below details
• Rel-8 UEs use only RSRP (Reference Signal Received Power) based measurements of LTE cells
• Rel-9 UEs perform RSRP and RSRQ (Reference Signal Received Quality) measurements
LTE Cell Selection Criteria
For Rel-8 UEs
For Rel-9 and above
: Srxlev > 0
: Srxlev > 0 & Squal > 0
Srxlev = Qrxlevmeas – (Qrxlevmin + Qrxlevminoffset) – Pcompensation
Squal = Qqualmeas – (Qqualmin + Qqualminoffset)
Pcompensation = max (PEMAX – PUMAX, 0) dB
QrxlevMin
:Minimum required RSRP level for cell selection (dBm)
Qrxlevminoffset
:Used only when camped in VPLMN
PEMAX
:Maximum Tx power a UE may use in uplink
PUMAX
:UE Class specific maximum UL Tx power
Squal
:Cell selection quality value (dB)
Qqualmeas
:Measured cell quality value (RSRQ)
Qqualmin
:Minimum required quality level in the cell (dB)
Qqualminoffset :Offset to Qqualmin for a higher priority PLMN while camped in a VPLMN
For the initial rollout, it is recommended to use only RSRP based measurements, RSRQ related parameters
are not broadcasted in SIB message.
Key parameters
Following are the parameters being set to drive the selection process in LTE.
Parameter
Value
Unit
QrxlevMin
-124
dBm
QrxlevMinoffset
0
dB
PEMAX
23
dBm
•
•
•
Above parameter setting will allow LTE capable UEs to always select LTE cell, if available, i.e.
measured RSRP level is better than -124 dBm
If above criteria is not fulfilled (no LTE coverage), UE will search for a GSM cell
For GSM cells, current cell selection criteria will be used, Rx Level > -105 dBm (As per
configuration in current network)
6.2.2 Cell Re-selection
6.2.2.1
Intra frequency Cell Re-selection
UE performs intra frequency measurements when
Srxlev <= Sintrasearch
Cell ranking criteria Rs for serving cell and Rn for neighbor cell for cell reselection is defined as
Rs = Qmeas, s + Qhyst
Rn = Qmeas, n – Qoffset
Qmeas, s
:Serving cells RSRP
Qmeas, n
:Neighbor Cell RSRP.
Qoffset :Offset for Neighbor Frequency
UE will perform reselection to intra-frequency neighbor cell if
Rn> Rs
RSRPneighbor - qOffsetCell > RSRPserving + qHyst
Key parameters
Parameter
Sintrasearch
Value
44
Unit
dB
Qhyst
3
dB
Qoffset
0
dB
Treseleutra
1
sec
With Sintrasearch = 44dB, UE will measure Intra-frequency neighbor cells when serving cell RSRP falls
below -80 dBm ( -124 + 44 )
UE will reselect to an intra-frequency LTE neighbour cell if neighbour cell RSRP is 3 dB better than serving
cell.
6.2.2.2
Inter Frequency and Inter RAT Cell Re-selection
Cell reselection between different LTE frequencies and different RATs is based on absolute priorities.
These can be configured for each LTE frequency (including serving cell) and for every frequency of each
RAT. Priorities are provided to UE via system information. UE performs cell reselection evaluation only
for those inter-LTE frequency and inter-RAT carriers for which UE has received priority.
UE performs inter-frequency or inter-RAT neighbor measurements when
Srxlev <= Snonintrasearch
Parameter
Value
Unit
QrxlevMin
-124
dBm
Snonintrsearch
10
dB
With Qrxlevmin as -124 dBm and Snonintrasearch as 10 dB, UE will start measuring inter-freq or interRAT neighbor when serving cell RSRP falls below -114 dBm (i.e.-124 + 10dB)
Reselection from a higher priority cell to a lower priority cell will be performed if
SservingCell < Threshserving,low AND the SnonServingCell,x > Threshx,low during a time
interval TreselectionRAT And More than 1 sec elapsed since the UE camped on the current
serving cell
Reselection from lower priority cell to higher priority cell will be performed if
Snonservingcell > Thresh,high during Treselection And More than 1 sec elapsed since the UE
camped on the current serving cell
LTE to GSM Cell Reselection
LTE is at higher priority compared to GSM
Parameter
QrxlevMin
Snonintrsearch
threshSrvLow
gerFrqThrL
qRxLevMinGer
Value
-124
10
8
0
-105
Unit
dBm
dB
dB
dB
dBm
UE will perform reselection from LTE to GSM if LTE serving cell RSRP < -116 dBm AND GSM
neighbour cell Rx Level > -105 dBm
GSM to LTE Cell Reselection
As LTE is higher priority layer, UE in GSM layer will always measure LTE layer.
UE will reselect from GSM to LTE if LTE cell RSRP > -112 dBm
GSM Parameters
lteAdjCellMinRxLevel
lteAdjCellReselectUpperThr
Value
-124
12
Unit
dBm
dB
There will not be any change in existing 2G-3G interworking parameters
6.3
Connected Mode Layering Strategy
6.3.1
Intra LTE Handover
Intra frequency handover can be based on event A3 or A5.
Event A3 based handover (better cell handover) aims to keep the UE always on the best cell. Event A3 is
triggered if
Neighbor cell RSRP > Serving cell RSRP + a3offset for specific time period (defined by time to
trigger parameter)
Parameter
Value
Unit
3
dB
a3-TimeToTrigger
320
ms
a3-ReportInterval
640
ms
a3-offset
Handover will get triggered when neighbor cell is 3 dB better than serving cell for at least 320ms time
duration.
Event A5 based Handover moves UE to other intra-frequency cell when serving cell RSRP gets below an
absolute threshold and neighbor cell RSRP becomes better than an absolute threshold.
Serving Cell < threshold3 AND
RSRP Neighbor cell > thresholds 3a
Parameter
enableCovHo
threshold 3
threshold 3a
a5-TimeToTrigger
a5-ReportInterval
Value
1 (true)
30
32
320
640
Unit
dB
dB
ms
ms
Based on above parameter setting, coverage based handover will trigger if serving cell RSRP falls below 110dBm and neighbor cell RSRP is better than -108dBm for 320ms time duration.
6.3.2 Inter RAT Data Handover
6.3.2.1
Inter RAT Handover - LTE to GSM
When leaving LTE coverage, Handover of data services from LTE to 2G can be enabled. This limits the
service interruption time to ensure minimal impact on end user experience. Event triggered handover is
based on downlink RSRP measurements reported by UE. Inter RAT measurements are triggered by event
A2. Handover decision is based on event B2.
Following measurement events are used
Event A2
Serving cell becomes worse than absolute threshold
: Activate IRAT measurements
Event A1
Serving cell becomes better than an absolute threshold) :Deactivate IRAT measurements
Event B2
Serving cell becomes worse than threshold1 and Neighbor cell becomes better than threshold2
Parameter in LTE Cell
Value
Actual Value
threshold2GERAN
23
-117 dBm
b2Threshold1GERAN
21
-119 dBm
b2Threshold2RssiGERAN
10
-105 dBm
threshold2a
36
-104 dBm
6.3.2.2
Remarks
Start IRAT Measurements
Redirection to 3G based on event B2
Stop IRAT measurements
Redirection without Measurements - LTE to GSM
When UE risks losing coverage and no handover is possible, eNB can redirect UE to target RAT/frequency
using RRC Connection Release message.
Based on event A2 reports, eNB triggers redirection towards specific RAT (GSM).
6.4
Parameter
Vale
Actual Value
threshold4
18
-122
LTE Voice
6.4.1
CSFB to 2G
As there is no CS domain in LTE, voice services can be provided by
1. VoLTE : Voice over IP (VoIP ) technique, requires IMS or
2. CSFB :UE will be moved to other RAT that provide CS domain
With CSFB, voice calls initiated in LTE can be redirected to either GSM or UMTS network
CSFB calls are redirected to GSM900 layer. Following table provides relevant parameters for CSFB
target RAT
Parameters
redrtId
actCSFBRedir
redirRat
Value
1
1
geran
Remarks
CSFB to GSM900
csFallBPrio
redirGeranArfcnValue
1
G900 ARFCN
.
6.4.2
Fast return to LTE
CSFB UE in 2G will be moved to 4G through fast reselection as per the feature activation in 2G RAT.
7. Paging
MME is responsible for sending paging records to the eNB using S1AP: Paging message. MME sends the
paging records to all eNode B with cells belonging to the relevant tracking area (idle mode UE location is
known on a tracking area basis). Paging records can originate from either the CS or PS core network
domains. CS pages traverse the SGs interface to reach the MME from the MSC. The eNode B collects,
schedules and broadcasts the individual paging records. Scheduling of paging records depends on paging
frames and paging occasion.
Key Paging definitions
•
DRX: UE in RRC Idle mode uses Discontinuous Reception (DRX) to reduce power consumption.
The DRX cycle determines how frequently UE check for paging messages. The default DRX cycle
is defined using the defPagCyc parameter
•
Paging Frames: UE listen for paging messages during their Paging Frames. Paging Occasions:
UE attempt to decode paging messages during specific subframes within their paging frames
defined by paging occasion (PO). The Paging Occasion defines a single subframe for each UE.
Following are the key paging parameters to be configured
Parameter
Value
defPagCyc
128
pagingNb
T
Remarks
128 radio frames in paging cycle => 1280ms DRX period
number of subframes (PO) used for paging within each radio frame
Maximum 16 paging records can be sent in one RRC Paging message. With nB set as ‘T’, max paging
capacity at eNB level will be 1600 pages per second.
8. Volte:
LTE has no Circuit Switched (CS) bearer to support voice, so carrying voice over LTE requires a
migration to a Voice over IP (VoIP) solution. Until this migration occurs, LTE-capable handsets need to
revert to 2G or 3G for voice calls, which can reduce quality or even suspend Packed Switched (PS)
services.
The IP Multimedia Subsystem (IMS) Profile for Voice and SMS document, commonly referenced as
Voice over LTE (VoLTE), defines the mandatory set of features that the mobile device and network are
required to implement in order to guarantee an interoperable, high quality IMS-based telephony service
over LTE.
8.1
Volte Architecture:
Below snap represent the Volte Network Architecture along with major network elements
8.2
•
Volte Bearer Combination:
The VoLTE service has specific bearer combination requirements.
-
QCI1 dedicated bearer is used for the speech.
-
QCI5 bearer is used for SIP signaling to the IMS.
QCI
Guarantee
Priority
Delay Budget
Loss Rate
Application
1
GBR
2
100 ms
1.00E-02
VoIP
2
GBR
4
150 ms
1.00E-03
Video call
3
GBR
3
50 ms
1.00E-03
Real time gaming
8.3
4
GBR
5
300 ms
1.00E-06
Streaming
5
Non-GBR
1
100 ms
1.00E-06
IMS signalling
6
Non-GBR
6
300 ms
1.00E-06
Streaming, TCP
7
Non-GBR
7
100 ms
1.00E-03
Interactive gaming
8
Non-GBR
8
300 ms
1.00E-06
9
Non-GBR
9
300 ms
1.00E-06
Streaming, TCP
Volte Parameter:
For activation of VOLTE below parameter setting is required
MOC
Abbreviated name
LNBTS
actConvVoice
Values
Description
range: {false, true}
Activates the support of conversational voice bearer
default: false
range:
{SIGNALLING,
NON-GBR}
schedulType
LNBTS
Specifies how the EPS bearer with QCI 5 is scheduled. In case of
Signaling the bearer is handle like SRB
default: NON-GBR
range: 0-400, step:
1
default: 100 (for
10MHz band)
LNCEL
maxNumQci1Drb
LNCEL
addNumQci1DrbRadioReasHo
range: 0-400, step:
1
default: 15 (for
10MHz band)
LNCEL
range: 0-400, step:
1
addNumQci1DrbTimeCriticalHo
default: 20 (for
10MHz band)
Threshold for the maximum number of established QCI1-GBRDRBs in the cell
Additional margin for the maximum number of active GBRs in the
cell accessing the cell via handover with HO-cause "HO desirable
for radio reasons". This margin is added to the threshold
maxNumQci1Drb.
Additional margin for the maximum number of active GBRs in the
cell accessing the cell via hand over with HO-cause: "Time
Critical HO". This margin is added to the threshold
maxNumQci1Drb.
QCI1 Specific parameters for different bandwidths are defined below
Carrier BW
20 MHz
15 MHz
10 MHz
5 MHz
max PRBs
100 PRBs
75 PRBs
50 PRBs
25 PRBs
PRBs for UL-signaling (PUCCH)
19
17
10
8
Parameter
range,
default
range,
default
range,
default
range,
default
step size
value
step size
value
step size
value
step size
value
maxNumQci1Drb
addNumQci1DrbRadioReasHo
addNumQci1DrbTimeCriticalHo
0…600
step 1
0…600
step 1
0…600
step 1
100
40
40
0…500
step 1
0…500
step 1
0…500
step 1
100
30
30
0…400
step 1
0…400
step 1
0…400
step 1
100
15
20
0…200
step 1
0…200
step 1
0…200
step 1
75
15
15
9. Single Radio Voice Call Continuity (SR-VCC)
The core network will need to support VoIP capable LTE handsets to continue voice calls even when the
user leaves LTE domain and a hand-over to 2G/3G. This functionality is called ‘single radio voice call
continuity (SR-VCC)’ and is, as CS-fallback, standardized in 3GPP R8. The standard further specifies
measures to ensure quality of service and a rich set of voice services. These standard functions ensure the
continuity of voice service when introducing LTE without impacting the end-user experience and enable
mobile operators to differentiate from plain internet voice offerings.
Single Radio Voice Call Continuity (SRVCC) 3GPP TS 23.216 refers to continuity between VoLTE in
PS access and CS calls that are anchored in MSS or IMS when the UE is capable of
transmitting/receiving on only one of those access networks at a given time
9.1
SRVCC to WCDMA/SRVCC to GSM
No new thresholds and time-to-trigger values are introduced for SRVCC features for triggering
the inter-RAT measurement procedures or triggering the actual handover
-
LTE442 eNACC related parameters are reused for SRVCC to GSM
-
LTE56 Inter-RAT handover to WCDMA parameters are reused for SRVCC to WCDMA